Optically readable tags encode data in an optically readable format. Some optically readable tags, such as bar codes, are considered to be one-dimensional in that the tags encode information in a format that can be read via a scan along one direction. Other tags are considered to be two-dimensional in that the tags encode information along two directions. In either case, such tags may be used to identify objects on which the tags are located.
The bit depth of an optically readable tag determines how much data can be encoded on the tag. Generally, the bit depth of a tag is proportional to a number of individual data features, such as individual lines of a bar code, located on the tag. Therefore, a tag with sufficient bit depth for uniquely identifying individual objects within a large set of objects either may have a relatively large size, or relatively small data features that are difficult to track optically via a machine vision system when the tag is in motion.